The influence of different referencing methods on the accuracy of δ13C value measurement of ethanol fuel by gas chromatography/combustion/isotope ratio mass spectrometry. (29th September 2015)

• Record Type: Journal Article
• Authors: Neves, Laura A.; Rodrigues, Janaína M.; Daroda, Romeu J.; Silva, Paulo R. M.; Ferreira, Alexandre A.; Aranda, Donato A. G.; Eberlin, Marcos N.; Fasciotti, Maíra
• Is Part Of: Rapid communications in mass spectrometry. Volume 29:Number 21(2015)
• Page Start: 1938
• Page End: 1946
• Publication Date: 2015-09-29
• Subjects: Mass spectrometry -- Periodicals; 543.65
• DOI: 10.1002/rcm.7298
• Languages: English
• ISSNs: 0951-4198

Abstract

<abstract abstract-type="main"> <title> <x xml:space="preserve">Abstract</x> </title> <sec id="rcm7298-sec-0001" sec-type="section"> <title>Rationale</title> <p>Brazil is the largest producer of sugar cane bioethanol in the world. Isotope ratio mass spectrometry (IRMS) is the technique of choice to certify the origin/raw materials for ethanol production, but the lack of certified reference materials (CRMs) for accurate measurements of δ<sup>13</sup>C values traceable to Vienna Pee Dee Belemnite (VPDB), the international zero point for <sup>13</sup>C/<sup>12</sup>C measurements, certified and compatible with gas chromatography (GC)/IRMS instruments may compromise the accuracy of δ<sup>13</sup>C determinations.</p> </sec> <sec id="rcm7298-sec-0002" sec-type="section"> <title>Methods</title> <p>We evaluated the influence of methods for the calibration and normalization of raw δ<sup>13</sup>C values of ethanol samples. Samples were analyzed by GC/C/IRMS using two different GC columns. Different substances were used as isotopic standards for the working gas calibration. The δ<sup>13</sup>C values obtained with the three methods of normalization were statistically compared with those obtained with elemental analyzer (EA)/IRMS, since the δ<sup>13</sup>C results obtained using EA are traceable to VPDB via the NBS 22 reference material.</p> </sec> <sec id="rcm7298-sec-0003" sec-type="section"> <title>Results</title> <p>It was observed that both the isotopic reference material for CO<sub>2</sub> calibration and the GC column have a major effect on the δ<sup>13</sup>C measurements, leading to a bias of almost 2–3 ‰ in the δ<sup>13</sup>C values. All three methods of normalization were equivalent in performance, enabling an improvement in the GC/C/IRMS accuracy, compared with the EA/IRMS reference values for the samples.</p> </sec> <sec id="rcm7298-sec-0004" sec-type="section"> <title>Conclusions</title> <p>All the methods of CO<sub>2</sub> calibration, chromatography and normalization presented in this work demonstrated several sources of traceability and accuracy loss for the determination of δ<sup>13</sup>C values in ethanol fuel samples by GC/C/IRMS. This work has also shown the importance of using proper CRMs traceable to VPBD that should be compatible and certified using GC/C/IRMS, ideally in a wide range of δ<sup>13</sup>C values. This is important not only for bioethanol fuel samples, but also for many analytes commonly analyzed by IRMS. Copyright © 2015 John Wiley & Sons, Ltd.</p> </sec> </abstract>